README: suggest ctest -V for getting started

Suggest that users run `ctest -V` instead of `make test` when getting
started.  `ctest -V` is superior over alternatives as:

1. Unlike `make test`, it gives output.  Users getting started with
   the library believe that it is hung.
2. `ctest -V` shows verbose output; showing suite names is helpful for
   giving users more feedback immediately.

Author: ethomson

README.md

@@ -135,7 +135,7 @@ Alternatively you can point the CMake GUI tool to the CMakeLists.txt file and ge
 
 Once built, you can run the tests from the `build` directory with the command
 
-	$ make test
+	$ ctest -V
 
 Alternatively you can run the test suite directly using,